Method for Extracting Random Signatures From a Material Element and Method for Generating a Decomposition Base to Implement the Extraction Method

ABSTRACT

The present invention concerns a method for extracting a random signature from a subject material element, comprising:
         a phase to generate at least one acquisition vector of structural characteristics of at least one region of the subject material element,   a phase to generate at least one random signature vector from the acquisition vector, the random signature vector comprising:
           at least one random component having a stable nature so that its value may be found on each implementation of the method on one same region of the subject material element,   and/or at least one random component having an unstable nature so that its value is likely to vary random fashion on each implementation of the method on one same region of the subject material element,   
           use of the random signature vector as random signature.

The present application claims the priority of French patentapplications FR 05/13231, FR 06/01342 and U.S. provisional application60/774,618 which are hereby incorporated by reference.

The present invention concerns the technical area of signatureextraction from a subject material element, either with a view toidentifying this subject material element, or with a view to using theextracted signature in a process dependent on the subject materialelement or independent of this subject material element.

The problem with the signature of a subject material element lies in theneed to guarantee the unicity of this signature, so as to be sure ornearly sure that two separate material elements will have two differentsignatures irrespective of the size of the sample of the two subjectmaterial elements.

The invention proposes achieving this objective of signature unicity byextracting this signature from structural characteristics of the subjectmaterial element. By structural characteristics of the subject materialelement is meant in particular the internal and/or external geometric ormorphological characteristics, optionally associated withcharacteristics of chemical or physicochemical composition, colour,structure or others related to their location in space on the subjectmaterial element. The structural characteristics used by the inventionare those which may be generated by stimulation of a material elementand acquired by one or more suitable sensors.

Therefore, the invention concerns a method for extracting a randomsignature from a subject material element, comprising:

-   -   application of a decomposition base,    -   a generating phase to generate at least one acquisition vector        of structural characteristics of at least one region in the        subject material element,    -   a decomposition phase of each acquisition vector in accordance        with the decomposition base to obtain an image vector containing        random components which each correspond to the contribution in        the acquisition vector of a decomposition vector belonging to        the decomposition base,    -   a generating phase to generate at least one random signature        vector which comprises the same number of components or less        than the number of random components in each image vector, each        component of the random signature vector being obtained by        extraction and/or processing of at least one random component of        at least one image vector,    -   use of the random signature vector as random signature.

According to the invention, the result of the method is qualified as arandom signature since, firstly, it has all the characteristics of asignature, and in particular that of unicity for each subject materialelement and more particularly for each region of the subject materialelement, and secondly the constituent components of the random signaturevector are near-independent and near-equiprobable, even independent andequiprobable.

The method of the invention therefore sets itself apart from othersignature generating methods in that the signature has a pure ornear-pure random nature and is extracted from a subject material elementvia a signal, preferably a two-dimensional multidimensional signalcalled <<image-signal>> after decomposition in a <<base>>, the baseitself possibly being generated from the same material element or from adifferent material element.

Unlike prior art methods, the method subject of the invention proceedsby reducing the image-signal without any major algorithmic operationbeing required after extraction.

The invention also concerns a method for extracting a random signaturefrom a subject material element, comprising:

-   -   generating phase to generate at least one acquisition vector of        structural characteristics of at least one region of the subject        material element,    -   a generating phase to generate at least one random signature        vector from the acquisition vector, the random signature vector        comprising:        -   at least one random component of a stable nature so that its            value is able to be found on each implementation of the            method on one same region of the subject material element,        -   and/or at least one random component of unstable nature so            that its value is likely to vary random fashion on each            implementation of the method on one same region of the            subject material element.    -   use of the random signature vector as random signature.

Generation of the random signature may be made by decomposition using adecomposition base as explained previously, or using any other methodsuitable for signal processing such as autocorrelation for example.Unlike the prior art, the random signature of the invention, inparticular regarding the stable part, is not dependent on the processingor algorithm used but on the very structure of the subject materialelement.

In one preferred embodiment, the random signature vector comprises atleast one stable random component and at least one unstable randomcomponent.

According to one characteristic of the invention, the generation phaseof at least one acquisition vector comprises the following steps:

-   -   generating at least one acquisition, according to an acquisition        window, of structural characteristics of one region of the        subject material element,    -   digitizing, over a scanning path, each acquisition into an        acquisition vector.

Insofar as a particular acquisition window is used, the method forextracting a random signature may comprise a determination step todefine the characteristics of the acquisition window. Therefore, duringthis step to determine the characteristics of the acquisition window, itis possible in particular to choose the dimensions and/or form of theacquisition window which then becomes a parameter for implementing therandom signature extraction method.

Similarly, insofar as a particular scanning path is used, the method forextracting a random signature may comprise a determination step todefine the characteristics of the scanning path. Therefore, during thestep to define characteristics of the scanning path, it may be chosen toread the data of the acquisition window in rows by horizontal scanning,or in columns using vertical scanning, or for example using acombination of vertical scanning and horizontal scanning.

According to one characteristic of the method for extracting a randomsignature, quantification is performed during the generation phase of arandom signature vector so that each random component of the randomsignature vector is able to present a finite number of values or levels.

According to another characteristic of the inventive method forextracting a random signature, during the generation phase of at leastone acquisition vector, n acquisition vectors are generated of one sameregion of the subject material element, and n image vectors are usedeach corresponding to an acquisition vector.

When using the n acquisition vectors of one same region of the subjectmaterial element and applying the decomposition of the acquisitionvectors into image vectors in the decomposition base, according to onecharacteristic of the random signature extraction method and during thegeneration phase of at least one random signature vector:

-   -   quantification is performed so that each random component of the        random signature vector is able to present a finite number of        values or levels of quantification which correspond to        statistical classes,    -   the value or level of each component of the random signature        vector is defined by the result of the tests and/or statistical        processing applied to all values of the component of a given row        of n image vectors.

According to another characteristic of the invention, during thegeneration phase of at least one random signature vector, the componentsof the image vectors undergo centred reduced statistical processing.

According to another characteristic of the invention, during thegeneration phase of at least one random signature vector:

-   -   the following are applied:        -   a number C of statistical classes corresponding to values or            levels able to be adopted by random components of the random            signature vector,        -   and a statistical class corresponding to the unstable nature            of the components of one same row of n image vectors,    -   to determine the value of each random component of the random        signature vector, statistical processing and a statistical        stability test are conducted on all the components of one same        row of the n image vectors, so that:        -   if, after the stability test, it appears that the components            of this row of image vectors show a stable nature, then the            value or level of the statistical class to which the            components of this row of the n image vectors belong is            assigned to the random component of the random signature            vector,        -   if, after this test, it appears that the components of this            row of image vectors show an unstable nature, then the value            or level of the statistical class to which the component of            this row of one of the n image vectors belongs is assigned            to the random component of the random signature vector.

According to a further characteristic of the invention, and for theimplementation of the above form of the method, during the generationphase of at least one random signature vector, the stability test isperformed on the basis of the mean and standard deviation of thecomponents of one same row of image vectors.

According to a further characteristic of the invention, the nacquisition vectors are generated virtually from a real number ofacquisitions less than n, even from only one real acquisition.

According to one characteristic of the invention, the random signaturevector, generated after the extraction method, comprises at least onerandom component having a stable nature, the value of this random stablecomponent being able to be found on each implementation of the method onone same region of the subject material element.

According to one characteristic of the invention, the random signaturevector, generated after the extraction method, comprises at least onerandom component having an unstable nature, the value of this unstablerandom component being likely to vary random fashion on eachimplementation of the method on one same region of the subject materialelement.

According to one characteristic of the invention, after the extractionprocess, all the random components of the random signature vector have astable nature, the value of each stable random component being able tobe found on each implementation of the method on one same region of thesubject material element.

According to one characteristic of the invention, after the extractionprocess, all the random components of the random signature vector havean unstable nature, the value of each unstable random component beinglikely to vary random fashion on each implementation of the method onone same region of the subject material element.

According to one characteristic of the method for extracting a randomsignature according to the invention, during the generation phase of atleast one random signature vector, the following are generated:

-   -   a stable random signature vector whose random components have a        stable nature, the value of each stable random component being        able to be found on each implementation of the method on one        same region of the subject material element,    -   an unstable random signature vector whose random components have        an unstable nature, the value of each unstable random component        being likely to vary random fashion on each implementation of        the method on one same region of the subject material element.

According to a further characteristic of the invention, and after theimplementation of the method for extracting a random signature:

-   -   the random signature vector comprises:        -   at least one random component having a stable nature so that            its value may be found on each implementation of the method            on one same region of the subject material element,        -   at least one random component which has an unstable nature,            so that its value is likely to vary random fashion on each            implementation of the method on one same region of the            subject material element.    -   during the generation phase of at least one random signature        vector, a reading mask is generated giving the position in the        random signature vector of the stable and/or unstable random        components.

The random signature or the random signature vector generated byimplementation of the inventive extraction method can be used indifferent manners, of which the following examples are non-exhaustive.

Hence, according to one characteristic of the invention, the inventivemethod for extracting a random signature comprises a phase which uses atleast part of the stable random signature as identifier of the subjectmaterial element or of an object associated with the subject materialelement in an access control process.

According to another characteristic of the invention, the inventivemethod for extracting a random signature comprises a phase using atleast part of the stable random signature to ensure full confidentialitye.g. as a one-time pad in a symmetric or asymmetric cryptographicprocess.

According to a further characteristic of the invention, the randomsignature extraction method of the invention, comprises a phase using atleast part of the stable random signature as instruction sequence or asidentifier of an instruction sequence in a control process for an logiccontroller or machine.

According to one characteristic of the invention, the method forextracting a random signature according to the invention comprises aphase using at least part of the stable random signature as variables orparameters of a computer program.

According to another characteristic of the invention, the randomsignature extraction of the invention comprises a phase using at leastpart of the stable random signature as one-time pad to encrypt variablesand/executable parts of a computer program.

According to another characteristic of the invention, the inventivemethod for extracting a random signature comprises a phase using atleast part of the unstable random components as identifier of thesubject material element or of an object associated with the subjectmaterial element, and a phase using at least part of the stable randomcomponents to securitize the identifier, in particular by using thispart of the stable random component as one-time pad for encrypting theidentifier to obtain a securitized identifier.

According to one characteristic of the invention, the inventive methodfor extracting a random signature comprises:

-   -   a phase using at least part of the unstable random components as        private key in a public key/private key cryptographic process,    -   a phase using at least part of the stable random components to        securitize the identifier, in particular by using this part of        the stable random components as one-time pad for encrypting the        private key to obtain a securitized private key.

According to a further characteristic of the invention, the inventivemethod for extracting a random signature comprises:

-   -   a phase using part of the unstable random components as private        key in a public key/private key cryptographic process,    -   a phase using part of the unstable random components as public        key in the public key/private key cryptographic process,    -   a phase using at least part of the stable random components to        securitize the identifier, in particular by using this part of        the stable random components as one-time pad for encrypting the        private key to obtain a securitized private key.

According to one characteristic of the invention, the inventive methodfor extracting a random signature comprises:

-   -   a phase using at least part of the unstable random components as        identifier of the subject material element or of an object        associated with the subject material element,    -   a cipher phase of the identifier using a public key/private key        cryptography process to obtain an enciphered or signed        identifier,    -   a phase using at least part of the stable random components to        securitize the identifier, in particular by using this part of        the stable random components as one-time pad for encrypting the        enciphered or signed identifier to obtain an enciphered and        securitized identifier.

Under the above variant, part of the unstable random components may beused as private key and, similarly part of the unstable randomcomponents may be used as public key.

Other examples of the use of a random signature or of a random signaturevector produced using the extraction method of the invention may befound in applications FR 2866139, WO 200578651, WO 2005122100, US2005262350, FR 2870376.

According to the invention, the decomposition base used for the randomsignature extraction method may be a pre-existing base or a basegenerated by the random signature extraction method of the invention.

Therefore, the invention also concerns a method for generating adecomposition base which can be used to extract a random signature froma subject material element, comprising the following steps:

-   -   generating N acquisition vectors of structural characteristics        of at least one region of at least one material element separate        from the subject material element and/or the subject material        element itself,    -   analysing all the acquisition vectors using statistical methods        to obtain the decomposition base formed of decomposition vectors        enabling a representation of each acquisition vector in the form        of an image vector, of which each component corresponds to the        contribution of a decomposition vector in the acquisition        vector,    -   analysing at least part of the decomposition vectors to identify        that or those decomposition vectors, called common or certain        contribution decomposition vectors, which will form the origin        of highly determinist and/or common components to all the image        vectors obtained when using the decomposition base,    -   saving the decomposition base,    -   optionally saving a reading mask which, in the decomposition        base, gives the position of the possible decomposition vectors        at the origin of determinist components and/or the position of        the decomposition vectors at the origin of random components.        According to one characteristic of the invention, the analysis        of the decomposition vectors comprises the following steps:    -   projecting each acquisition vector onto the decomposition base        to obtain an image vector of which each component corresponds to        the contribution of a decomposition vector in the acquisition        vector,    -   analysing at least part of the image vectors to identify that or        those components which are highly determinist and/or common to        all the image vectors, the determinist components corresponding        to decomposition vectors in the decomposition base that are        called common or certain contribution decomposition vectors, the        other components of an image vector being considered as random        components.

According to one characteristic of the invention, it is considered thata component is of highly determinist nature if its value is predictablein relation to the type of the material element.

According to another characteristic of the invention, each acquisitionvector is preferably at least of two-dimensional nature.

According to another characteristic of the method for generating adecomposition base of the invention, the generating method comprises aremoval step to remove common or certain contribution decompositionvectors from the decomposition base, and a step to save the reduceddecomposition base called a decomposition base into random components.

According to a further characteristic of the inventive method forgenerating a decomposition base, the generating step to generateacquisition vectors is performed with at least one material element ofthe same family as the subject material element used in the randomsignature extraction method.

According to another characteristic of the inventive method forgenerating a decomposition base, the step to generate acquisitionvectors comprises the following steps:

-   -   generating a number N of acquisitions, according to an        acquisition window, of structural characteristics of at least        one region of at least one material element separate from the        subject material element and/or of the subject material element        itself,    -   digitizing, along a scanning path, each of the acquisitions into        the form of an acquisition vector.

As for the random signature extraction method, the method for generatinga decomposition base may comprise a step to define the characteristicsof the acquisition window. Therefore, according to one variant of theinvention; the method for generating a decomposition base comprises areading step to read the characteristics of the acquisition window.Similarly, the method for generating the decomposition base may alsocomprise a step to save the geometric characteristics of the acquisitionwindow.

Similarly, the method for generating a decomposition base may alsocomprise a step to define the characteristics of the scanning path. Themethod for generating a decomposition base may then comprise a readingstep to read the characteristics of the scanning path, and a step tosave the characteristics of the scanning path used for the digitizationstep.

According to one characteristic of the invention, the method forgenerating a decomposition base, In order to obtain the decompositionbase, uses a Principal Component Analysis algorithm.

According to another characteristic of the invention, the method forgenerating a decomposition base, in order to obtain the decompositionbase, uses an Independent Component Analysis algorithm.

According to yet another characteristic of the invention, the method forgenerating a decomposition base, in order to identify deterministcomponents, uses a spectral decomposition algorithm and identificationof certain contribution decomposition vectors by filtering.

According to one characteristic of the method for generating adecomposition base, also applicable to the method for extracting arandom signature from a subject element material, each material elementused is chosen from among: materials of dead biological origin,materials of organic origin, materials of mineral origin or materialsobtained by mixture and/or composition and/or deposit of several of thepreceding materials.

Evidently, the different characteristics of the random signatureextraction method may be combined with each other in different mannersinsofar as they are not incompatible with each other.

Similarly, the different characteristics of the method for generating adecomposition base may be combined with one another in different mannersinsofar as they are not incompatible with each other.

The present invention also concerns an apparatus or device comprisingacquisition means, processing means and memory means, the processing andmemory means at least being adapted to implement the random signatureextraction method and/or the method for generating a decomposition baseaccording to the invention. According to the invention the device mayfurther comprise communication means.

The present invention also concerns a computer program being adapted toimplement the random signature extraction method and/or the method forgenerating a decomposition base according to the invention.

Various other characteristics of the invention will become apparent fromthe description given below, referring to the appended drawings whichillustrate non-limiting examples for implementing the methods that arethe subject of this invention.

FIG. 1 is a schematic view of an installation or device for implementingthe methods for generating a decomposition base and for extracting arandom signature from a material element.

FIG. 2 is a schematic view of the acquisition surface of a matrix sensorand of an acquisition window used for the inventive methods.

FIG. 3 is a summary diagram of the conducting of a decomposition basegenerating method according to the invention.

FIGS. 4 et 5 show examples of the scanning path which can be used forthe generating and extracting methods of the invention.

FIGS. 6 to 8 show examples of parts of decomposition bases generatedusing the inventive method.

FIG. 9 illustrates the form of the acquisition window used to generatethe base such as illustrated FIG. 8.

FIG. 10 illustrates another form of the acquisition window which may beused in a variant of the methods for generating a decomposition base andextracting a random signature according to the invention.

FIG. 11 is a summary diagram of the conducting of a method forextracting a random signature according to the invention.

FIG. 12 illustrates a classification and quantification step used in therandom signature extraction method described with reference to FIG. 11.

FIG. 13 gives a digital image (13A) in transvision of part of a sheet ofpaper, and a view (13B) giving the result of statistical processingapplied to the random signature extracted from the sheet of paper usingthe inventive method.

FIGS. 14 to 17 illustrate examples of use of part of the stable randomcomponents that are constituent parts of a random signature extractedusing the inventive method.

FIGS. 18 to 21 illustrate examples of use of part of the stable andunstable random components that are constituent parts of a randomsignature extracted using the method of the invention.

As mentioned previously, the invention concerns a method for extractinga near-pure, partly or fully stable, random digital signature from asubject material element 1 having a time-stable microstructure, partlychaotic, revealed by physical, chemical, biological or other stimulatingaction. The invention also concerns the use of this signature to producerandom sequences for example, or private keys, pairs of public/privatekeys, self-protected identifiers of subject element 1.

According to the invention, the constituent material of subject materialelement 1 may, for example, be of dead biological origin, organic, ormineral origin or result from the mixture, composition or deposit ofmaterials of dead biological, organic or mineral origin. The constituentmaterial of subject material element 1 is chosen for the time-stablechaotic nature of its microstructure which is intended to be revealed byphysical, chemical, biological or other stimulation.

Some materials, such as paper, intrinsically contain a structure that isat least partly chaotic arising from the variability of theircomponents, the variability in their arrangement and/or complexity ofmanufacturing process. According to the illustrated embodiment of theinvention, subject material 1 is a sheet of paper.

The invention sets out to extract or acquire at least part of thestructural characteristics of subject material element 1 which giveinformation on the complexity or chaotic structure of its structure. Forthis purpose one or more, preferably non-destructive, stimulations,chosen according to the type of subject material element 1 are appliedto at least part of subject material 1. The stimulation may derive frommechanical action, a light ray source or another other physical source.The response to this stimulation by subject material element 1 is thenrecorded by means of an appropriate sensor chosen according to the typeof stimulation made and the type of subject material element 1.

For a translucent material such as paper, physical stimulation may beapplied by a light source which emits a light ray whether coherent ornot, polarized or not, illuminating a piece of paper in transmission orreflection, the image corresponding to the response of the material tolight stimulation then possibly being acquired using a digital camera.

Hence, according to the illustrated example, subject material element 1,consisting of paper, is illuminated by means of a lamp 2 emittingincoherent white light. The image resulting from transmission of whitelight by part 3 of subject material element 1 is acquired using a matrixsensor 4 integrated in a camera 5 linked to a processing unit 5 ₁.

The form of that part 3 of subject material element 1 whose image isacquired by sensor 4, is defined by the form of an acquisition windowwhose limits or boundaries are fixed either by the form of the sensor,or by the form of a diaphragm whether adjustable or not, or byprocessing applied to the signal derived from sensor 4 so that solelypart of the data is kept. For example, if the surface of sensor 4 is ofrectangular shape such as illustrated FIG. 2 the limits of theacquisition window, in the absence of processing and diaphragm,correspond to the physical limits of the sensor surface. However,according to the invention, it may be chosen to define an acquisitionwindow whose limits or form do not correspond to those of the sensor 4.For example, an acquisition window 6 may be chosen which onlycorresponds to part of the sensor and is of irregular shape such asillustrated by the dotted lines in FIG. 2. This acquisition window 6 maythen result either from the positioning of a physical diaphragm insertedbetween the subject material element 1 and the sensor 4, or fromprocessing applied to the signal from the sensor 4.

Evidently, the form of the acquisition window 6 illustrated FIG. 2 isnot limitative and any other shape could be adopted. Hence, acquisitionwindow 6 is not necessarily unitary or in one piece but may correspondto separate regions distant from each other. Similarly the shape of theacquisition window is not necessarily planar or two-dimensional but mayalso, in relation to the sensor and/or stimulation, correspond to avolume or to a mathematical object with more than three dimensions. Theshape of the acquisition window in its broad meaning, namely theappearance of its limits or boundaries, its position, its orientation,form an input data item or a parameter for implementation of theinvention both regarding the method for generating a decomposition baseand the method for extracting a random signature.

Under the principle of a preferred embodiment, the random signatureextraction method of the invention sets out to decompose the imagesignal of the predefined region 3 of subject material element 1 into asum of elementary mode contributions, each contribution consisting of amode to which a scalar or component weight is assigned. In the imagesignal some of these modes may translate the presence of certainevolutionary physical phenomena described by Partial DerivativeEquations such as diffusion or propagation. Said modes may in particularform the own particular modes of a space operator (e.g. Laplacian) anddepend on the boundary of the predefined investigation regions, namelythe form of the acquisition window in its broadest meaning.

All the modes which can be used for description of the image signal,i.e. its decomposition, called decomposition base, may or may not beovercomplete. The decomposition base may be fixed or adapted to theimage signal. Adapted bases may derive from an analysis of projectionpursuits, in particular a component analysis which may or may not bebased on decomposition of singular value decomposition type such asPrincipal Component Analysis (PCA) or PCA-related such as IndependentComponent Analysis (ICA) or any other analysis close to PCA or ICA (e.g.ACP scattered PCA).

The random signature extraction method of the invention therefore uses abase B, optionally overcomplete, which may or may not be generated infull or in part from a first material element whether or not of the samefamily of elements as the subject material element, or from the subjectmaterial element itself.

Insofar as the use of a decomposition base particularly adapted to therandom signature extraction method of the invention is able to achievebetter extraction of the desired random signature, the invention alsoconcerns a method for generating a decomposition base B which can beused to extract a random signature from a subject material element.

FIG. 3 shows the steps for generating the decomposition base B from amaterial element E.

During a first step G1, N different regions of the material element Eare the subject of an acquisition (static or relative movement) and arethen digitized using a device D such as illustrated FIG. 1. During thisfirst step G1 N acquisition vectors are therefore generated ofstructural characteristics of N regions 3 of subject material element 1,wherein N is 2 or more and preferably much higher than 2.

If a matrix sensor 4 is used comprising a number M of cells, on eachacquisition the camera delivers an acquisition vector comprising Mcomponents; when the acquisition window 6 has a smaller surface than thesensor 4, as illustrated FIG. 2, the generation phase G1 comprises astep to reduce the acquisition vector derived from the camera 5 so thatit only comprises the m components concerning acquisition window 6,wherein M≧m. Also, the arrangement of the components in each acquisitionvector depends on the direction of scanning or on the scanning path, forexample horizontal scanning starting with the upper left cell asillustrated FIG. 4 or vertical scanning starting with the lower leftcell as illustrated FIG. 5, or any other form of scanning path such as aPeano curve. According to the invention, the configuration of thescanning path may form a parameter for implementation of the method forgenerating the decomposition base. Insofar as a random signature isextracted that is at least partly stable or reproducible, the samescanning path is preferably used for the decomposition base generatingmethod and on each implementation of the extracting method.

The characteristics or configurations of the acquisition window and thecharacteristics of the scanning path define what may be called theacquisition structure forming parameters for implementation of thedecomposition base generating method.

Intended to acquire the organisation of the stimulated microstructure,the N acquisition vectors so formed are preferably at least of twodimensional type, and are considered to represent a family of materialelements.

During the following step G2 an analysis is made of all N acquisitionvectors using a method for obtaining characteristic elementary modesdescribing the data. Each acquisition vector may then be represented bythese modes, each mode making a more or less important contribution. Themodes are vectors enabling the decomposition of each acquisition vectorinto the form of a contribution sum, each contribution consisting of adecomposition vector to which a scalar or component weight is assigned.All the components form an image vector describing the acquisitionvector under consideration. Therefore, the acquisition vectors form thecolumns of a data matrix which can be expressed as the product of thematrix of decomposition column-vectors, also called base vectors ordecomposition vectors, by the matrix of the image column-vectors.

Generally, analysis methods which build bases adapted to data arecandidate methods able to be used by the invention. Principal ComponentAnalysis (PCA) and its variants form part thereof. Centred-reduced PCA,by decomposing the matrix of centred reduced acquisition vectors intosingular values, delivers the orthogonal matrix of the base vectors ordecomposition vectors. The image vectors are deduced therefrom by simpleprojection of the acquisition vectors onto this base. The components ofthe image vector then have the property of being centred andde-correlated;

Independent Component Analysis (ICA) which provides the same type ofanalysis as PCA (in that the components of the image vector obtainedhave the property of being centred, de-correlated and evennear-independent), may also be used. The decomposition vectors and theimage vectors are obtained simultaneously, e.g. by maximizing thenon-Gaussianity of the components of the image vector. Differentalgorithms meet this criterion depending upon implantation (FastICA,JADE, InfoMax, . . . ).

All the decomposition vectors then form a decomposition base B which canbe used for the inventive method of extracting a random signature from asubject material element. For this purpose, the decomposition base B maybe stored or saved so that it can be used on request when implementingthe random signature extraction method of the invention, on theunderstanding that this method may also provide for the generation of adecomposition base B as explained previously on each extraction of arandom signature.

When generating the decomposition base, it may also be considered toproceed with analysing at least part of the image vectors to identifythat or those components which are highly determinist and/or common tothe majority of and even all the image vectors, the deterministcomponents corresponding to decomposition vectors in the decompositionbase, called common or certain contribution decomposition vectors, theother components of an image vector being considered as randomcomponents. At the end of this analysis either a reading mask is savedwhich, in each image vector, gives the position of any deterministsand/or the position of any random components, or a reduced decompositionbase is saved whose determinist decomposition vectors have been deleted.

FIG. 6 illustrates an example of decomposition base generation madeusing images of a piece of paper illuminated by transmission inincoherent light with a square-shaped acquisition window, and a scanningpath of horizontal scanning type such as illustrated FIG. 4. Generationof the base has also been made using Principal Component Analysis (PCA).Part 6A in FIG. 6 is a graph showing the PCA spectrum (all own values)while part 6B shows 25 base elements belonging to the second third ofthe spectrum.

Similarly, FIG. 7 illustrates an example of decomposition basegeneration, made using images of a piece of paper illuminated bytransmission in incoherent light, with a square-shaped acquisitionwindow and a scanning path of vertical scanning type such as illustratedFIG. 5. Generation of the base has also been made by Principal ComponentAnalysis (PCA). Part 7A in FIG. 7 is a graph showing the PCA spectrum,whilst part 7B shows 25 base elements belonging to the second third ofthe spectrum.

FIG. 8 illustrates another example of the generation of a base madeusing images of a piece of paper illuminated by transmission inincoherent light with a non-square shaped acquisition window,illustrated FIG. 9 and a scanning path of horizontal scanning type suchas illustrated FIG. 4. Generation of the base has also been made usingPrincipal Component Analysis (PCA). Part 8A in FIG. 8 is a graph showingthe PCA spectrum, whilst part 8B shows 25 base elements belonging to thesecond third of the spectrum.

According to one variant of implementation of the decomposition basegenerating method, the acquisition window 6 a used consists of a numberi of elementary windows 6 ₁ identical and not joined together as shownFIG. 10. According to the illustrated example, window 6 a comprises 12elementary windows 6 ₁ of rectangular shape (i=12). Generation of thedecomposition base then uses a phase to generate an elementarydecomposition base whose elementary decomposition vectors are generatedusing the previously described method applied to elementary windows 6 ₁taken individually, an acquisition of window 6 a then being treated as iacquisitions of an acquisition window that is identical to an elementarywindow 6 ₁. During the generation phase of the elementary decompositionbase, the elementary windows 6 ₁ and their acquisitions are thereforeconsidered to be independent from one another, so that the generatedelementary decomposition base allows the decomposition of eachelementary acquisition corresponding to an elementary acquisition window6 ₁ into an elementary image vector with random components whosecomponents correspond to the respective contributions of the elementarydecomposition vectors. To obtain a decomposition base which can be usedfor acquisition window 6 a taken as a whole, the generation of thedecomposition base then uses a step to create the decomposition basefrom the elementary decomposition base by forming each decompositionvector by concatenation of i times one same elementary decompositionvector. Therefore, the decomposition base comprises the same number ofvectors as the elementary decomposition base, and if each elementarydecomposition vector comprises j components then each decompositionvector will comprise i×j components

A decomposition base generated according to either one of the abovevariants of the inventive generating method can then be used with arandom signature extraction method according to the invention.

In a preferred embodiment, the method for extracting a random signaturefrom a subject material element 1, as arises from FIG. 11, comprises thefollowing phases.

First, if the decomposition base B is not generated when extracting therandom signature, a pre-recorded decomposition base B is chosen whichwill be used for extraction. Optionally the decomposition base B isassociated with characteristics of an acquisition window 6 and of ascanning path which may be used for extracting the random signature.

Then a generation phase I is conducted to generate at least one andpreferably n acquisition vectors of structural characteristics of region3 of subject material element 1, wherein n is 2 or more and preferablymuch higher than 2. The generation of the acquisition vectors may bemade using an acquisition window 6 or 6 a such as defined previously.When it is desired to extract a stable or reproducible random signaturefrom an object material element 1, the same acquisition window or thesame window acquisition parameters are used for each implementation ofthe inventive method, these parameters preferably being those of theacquisition window optionally associated with decomposition base B.

When using a matrix sensor 4 comprising an M number of cells, the cameradelivers an acquisition vector comprising M components; if theacquisition window 6 has a smaller surface than the sensor 4; asillustrated FIG. 2, the generation phase I comprises a step to reducethe acquisition vector derived from camera 5 so that it only containsthe m components concerning acquisition window 6, wherein M≧m.

Also, the arrangement of the components in each acquisition vectordepends on the direction of scanning or on the scanning path, e.g.horizontal scanning starting with the upper left cell as illustratedFIG. 4 or vertical scanning starting with the lower left cell asillustrated FIG. 5, or any other form of scanning path. According to theinvention, the configuration of the scanning path may form a parameterfor implementation of the extraction method. Insofar as a randomsignature that is at least partly stable or reproducible is extracted,the same scanning path will be used for each implementation of themethod, and if the decomposition base is associated with a scanningpath, it is this latter path which is preferably used.

The characteristics or configurations of the acquisition window and thecharacteristics of the scanning path define what may be called theacquisition structure.

Phase I therefore entails the generation of n acquisition vectors. Thesen acquisition vectors then correspond either to n separate realacquisitions, or to one real acquisition from which n acquisitionvectors are generated. If the acquisition window 6 has a smaller surfacethan the sensor 4 it is possible to generate an acquisition vectorcorresponding to the real acquisition and n−1 acquisition vectorsgenerated by simulating micro-displacements of the acquisition window 6relative to the sensor 4, these micro-displacements corresponding topositioning errors of subject material element 1 during its successiveplacing n−1 times in the digitization device D which, according to theillustrated example, comprises the light source 2 and camera 5.

This set of acquisition vectors may, by averaging, be used to reduce theacquisition noise with real acquisition vectors resulting from the noiseof the camera 5 and the radiation source 2 and, in the case ofcalculated or synthesized acquisition vectors, the noise which may becaused by repositioning of subject material element 1.

After phase I there are n column acquisition vectors each comprising mcomponents which therefore form a matrix with m rows and n columns.

A phase II is then conducted to decompose each acquisition vector,according to a decomposition base B containing decomposition vectors,into random components to obtain n image vectors which each comprise anumber m′ of components wherein m≧m′.

The decomposition base used may for example be a pre-existing baseoptionally created from material elements of same type as the subjectmaterial element, or a base created from the subject material element byanalysing several regions of the latter as described previously.

On completion of phase II we therefore have an image matrix comprisingm′ rows and n columns. This image matrix is used for following phase IIIto generate at least one random signature vector, phase III according tothe illustrated example comprising three steps IIIa, IIIb, IIIc.

The first step IIIa of phase III, is a step to reduce the image matrixby removing overactive image vectors from the components—called invalidimage vectors—and which therefore do not conform to the search for apurely random component for the signature vector. The activity of acomponent of a given row may be measured by analysing one row in theimage matrix. Measurement may be statistical after estimating thehistogram of the previous row. It may also be defined as the energy of arow. The decision to remove an invalid component can be taken withrespect to the other components after evaluating the activity of each ofthe components. A reduced image matrix is then obtained, comprising nreduced image vectors which each have m″ components wherein m′≧m″.

Step IIIb classifies the components of the image vectors of the reducedimage matrix, leading to the qualification of their stable or unstablenature. For this purpose and as schematically illustrated FIG. 12, theaxis of values x-x′ associated with each of these components is dividedinto different predefined statistical classes c which will be used forquantification into (discrete) levels during subsequent step IIIc. If agiven component, corresponding to one row of the matrix, is consideredto belong to one of these classes—called quantification classes—it isthen declared stable. The inclusion in said class may be determinedafter statistical analysis of the row corresponding to the component.This analysis may proceed with estimating the histogram of the rowfollowed by an estimation of its mean values and standard deviation. Theinclusion in the class under consideration can be considered true whenthe histogram s is almost completely contained in the class underconsideration (e.g. the mean centred interval, of equal width to acertain number of times the standard deviation, is fully contained inthe class). If the histogram i is <<equi-distributed>> between twoclasses, the component is considered unstable and allocated to anotherclass called the unstable class. Finally, if the histogram Ø isdistributed over several classes or over two classes dissymmetricfashion, the component is generally considered to be unfit and isallocated to a so-called unfit class.

Following step IIIc carries out quantification (or assignment ofdiscrete levels among a finite group of numbers) of stable or unstable(valid) components. During this step, the unfit components (i.e.belonging to the unfit class) are not processed (considered as absentterms or <<holes>> in the image matrix) and do not give rise to anycomponent in the signature vector which will then contain m′″components, wherein m″≧m′″.

The stable components are given the level of quantificationcorresponding to their class (stable). For example, when the acquisitionvectors are centred reduced, a quantification on two levels orbinarisation can be conducted by assigning level 1 to a positivecomponent and level 0 to a negative component.

The unstable components have a value which may be any value, in whichcase the corresponding component of the signature vector will be giventhe value of the class corresponding to the value of the component for apredefined image vector. For example, when the acquisition vectors arecentred reduced and quantification on two levels or binarisation ismade, an unstable component is assigned a binary level, 0 (for example)if the value of the component in a predefined image vector (for examplethe first) is negative, 1 if it is positive.

A reading mask identifying or separating the stable components from theunstable components in the signature vector can then be generated duringstep IIIc.

Therefore, according to the illustrated example, on completion of phaseIII generating a random signature vector, a reading mask M is obtainedand a random signature vector V. In the present case, the reading mask Mis a vector comprising the same m′″ number of components as the randomsignature vector V. A component of the reading mask has a value 0 forexample when the corresponding component of the random signature vectorV is unstable, and a value 1 when the corresponding component of therandom signature vector V is stable.

Each component of the random signature vector V derives from a randomcomponent of an image vector considered to be valid after step IIIa, andstable or unstable after step IIIb.

Parts C in FIGS. 6 to 8 each show an extract of a binary sequencebelonging to a random signature obtained with the extraction method ofthe invention using the decomposition base decomposing into randomcomponents, of which part of the elements or vectors is shown in part Bof the corresponding figure.

By way of example, the random signature extraction method was applied toa piece of paper illuminated by transmission in incoherent light using adecomposition base generated from another piece of paper. Statisticaltests were performed on the components of the random signature vector V,comprising a sequence of 66 048 bits extracted from images of paper witha resolution of 3200 dpi, in order to determine the quality of thesignature extracted using the inventive method. Results were as follows:

Entropy=1.000000

Optimum compression ratio=0

Chi² distribution=0.79

Mean arithmetic value=0.5001.

Error on Monte-Carlo value for Pi=0.05

Series correlation coefficient=−0.000385

Since the inventive method generates a signature which is an image ofthe material structure of the subject material element, these resultsassociated here with knowledge of the chaotic nature of the papertranslate the purity or random nature of the random signature vector Vgenerated by the inventive method.

Similarly, the very strong random nature of the random signature vectorV is shown indirectly in FIG. 13, with the random search for primenumbers in a random signature of 9 200 000 bits extracted using themethod of the invention from a piece of paper of A4 format, and byperforming a succession of 20 primality probabilist tests calledMiller-Rabin tests.

Part 13A in FIG. 13 corresponds to an image of a square area, with sidesof 2 cm, of a standard sheet of paper illuminated by transmission withincoherent light. Part 13B in FIG. 13 corresponds to the representationby white dots of the first 100 prime numbers extracted from a randomsignature among the 125×(86−1) prime numbers of 18 bits represented inthe form of a black image of 125×86 pixels. Observation of part 13Bb inFIG. 13 shows the uniformity of the distribution of numbers found in allprime numbers, here of 18 bits, a uniformity which results from therandom nature of the signature extracted using the method of theinvention.

Also, it is to be noted that when implementing the inventive extractionmethod, the value of the stable part of the extracted random signaturemay be influenced by the following factors:

-   -   the subject material element and in particular the region of the        subject material element from which the random signature is        extracted,    -   the form of the acquisition window, and in particular its        position and orientation,    -   the form of the scanning path,    -   and the decomposition base used, in particular the material        element (or material elements) which may have been used to        generate the decomposition base, if different from the subject        material element.

The factors may therefore form as many parameters for implementing therandom signature extraction method of the invention.

Therefore, although conventionally treated as noise, that part of theimage signal corresponding to the chaotic content of the subjectmaterial element is, according to the invention, used in such manner asto extract a random signature i.e. a priori unpredictable. Thecomponents of the random signature vector V are therefore unpredictableboth as a whole but also one from another. It is also to be pointed outthat the random signature of the invention finds its origin in thestructure of the material of the subject material element and not in thealgorithms or processing operations used, which means that the inventionextracts the signature with a minimum number of processing operations soas to preserve the intrinsic structural characteristics of the subjectmaterial element. In addition, the signature of the invention has adigital nature i.e. it consists of components with values quantified infinite number or <<levels>>. All the components of the signaturetherefore form a near-pure random sequence of levels which may be usedas such, or to generate a random germ in any areas where it is necessarysuch as for identification, certification, traceability, cryptography,in particular for authentication, the generation of private keys and/orpublic keys, the securitization of data, secret-sharing, forsteganography but also for computing, or in robotics for simulating orcommanding random events (computer games, programming, . . . ).

As described previously, the method subject of the invention qualifieseach component of the random signature as stable or unstable. Asignature component is declared stable when its level can re-occur withstrict or near-strict identicality and very high probability after anynew stimulation of the material element, under identical or similarconditions. An error detector/corrector code can then be used toincrease the stability of the components, in particular for datasecuritization or accessing.

A random signature extracted using the method of the invention can beused in different manners.

Through the stable components which may be extracted therefrom, thematerial element may be used as a possessor's physical key. The stablerandom components may also be used to produce a One Time Pad or togenerate an identifier particular to the material element.

FIG. 14 illustrates one use of the stable components Vs of a randomsignature generated from a subject material element 1 using theextraction method P of the invention to ensure the protection ofessential variables or parameters 10 of a computer program 11. For suchuse, the stable random signature Vs is used as one-time key in anencrypting process 12, e.g. of XOR type, to obtain securitized essentialvariables 13. It is therefore possible to protect these essentialvariables with the stable random derived from material element 1 and tosubject the proper execution of the program to the presence of theauthentic material element in an acquisition system, not shown, linkedto a computer, also not shown, which runs the computer program 11 usingthe essential variables. The subject material element 1 is then neededto decrypt the securitized essential variables 13 and to revert to theessential variables 10 used by the computer program 11.

FIG. 15 shows one use of the stable components Vs of a random signaturegenerated from a subject material element 1 using extraction method P ofthe invention to control access to premises, machines, activities oreven information. According to this example of use, the stable randomsignature Vs is used as identifier and is compared by means of astatistical comparison process 14 with the content of a database Bd ofauthentic identifiers to authorize access 15 if the result of comparisonis positive.

FIG. 16 illustrates a further use of the stable components Vs of arandom signature generated from a subject material element 1 using theextraction method P of the invention to command a programmable logiccontroller 16. According to this example of use, the logic controller 16acts in relation to random instructions 17 derived from the stablerandom signature Vs. The actions performed by the logic controller 16may be of various kinds such as those corresponding to machining,weaving, displacement, opening or closure, dosing of elements or thepiloting of other logic controllers or machines, without this list beingconsidered as exhaustive.

It could also be considered to associate the stable random signature Vswith predefined actions via a correspondence data base relating valuesof stable random components to one or more sequences of instructions.

Along the same principle, it could be considered to control thefunctioning of a computer program using a stable random signature Vs. Inthis case, either one part of the components of the stable randomsignature corresponds directly to parameters of the computer program, ora correspondence base is used between the stable random components andpredefined parameters for the computer program.

FIG. 17 illustrates one use of stable components Vs of a randomsignature generated from a subject material element 1 using theextraction method P of the invention, to ensure the protection of datasuch as traceability data for example 17 intended to be associated witha product. For this type of use, the stable random signature Vs is usedas onetime key in an encrypting process 18, of XOR type for example, toobtain from traceability data 17 securitized traceability data 19 whichmay be affixed to the product. For said use, the subject materialelement 1 at the origin of the stable random signature Vs may be joinedto the product carrying the securitized information, in which casesecuritization will lie in the acquisition device which is to ensuredecrypting of the securitized data 19. This securitization will belinked in particular to the decomposition base used, in the form of theacquisition window or the scanning path which may be kept secret and beknown to the manufacturer alone of the acquisition device. Or on thecontrary it could be contemplated that the subject material element atthe origin of the stable random signature Vs is independent of theproduct and is held for example by the user in charge of verifying theauthenticity of the product carrying the securitized data 19.

As mentioned previously, a random signature V generated using theextraction method of the invention, may comprise unstable components ormay even only consist of unstable components, in which case it may beconsidered to use the extraction method of the invention as generator ofrandom numbers.

The unstable components of the random signature may be used to generateone or more identifiers and/or one or more private keys, each beingprotected by stable random components, e.g. via one or more one-timepads.

Insofar as a random signature of the invention may comprise both stablecomponents and unstable components, advantage may be drawn from thischaracteristic for various applications of which some non-exhaustiveexamples are given below.

FIG. 18 illustrates an example of use of a random signature V,comprising stable components Vs and unstable components Vi, generated bythe extraction method and, according to the invention, from a subjectmaterial element 1 in order to provide a securitized identifier 20. Withthis type of use, the unstable part Vi of a random signature V is usedas identifier, whilst the stable part Vs is used as one-time key in anencrypting process 21, e.g. of XOR type, to obtain the securitizedidentifier 20. The holding of the subject material element 1 and of adevice implementing the extraction method of the invention makes itpossible to re-access the stable part Vs of the random signature V andhence to decrypt the securitized identifier 20 to access the initialidentifier, in this case an unstable part Vi of a random signature Vgenerated at the time of assignment of the identifier.

FIG. 19 illustrates another example of use of a random signature V,comprising stable components Vs and unstable components Vi, generated bythe extraction method P of the invention from a subject material element1 to provide public and private keys, even pairs of keys in anasymmetric cryptographic protocol. For this type of use, the extractionmethod P is implemented a first time to generate a random signature V ofwhich part Vi1 of the unstable components is used as private key 25whilst another part Vi2 of the unstable components is used as public key26. Part of the stable components Vs is then used as one-time key in anencrypting process 27, e.g. of XOR type, to obtain from private key 25 asecuritized private key 28. Holding of the subject material element 1and a device implementing the extraction method of the invention thenmakes it possible to re-access the stable part Vs of the randomsignature V and hence to decrypt the securitized private key 28 toaccess the private key 25 generated during the first use of theinventive method P for extracting a random signature.

FIG. 20 illustrates another example of use of a random signature V,comprising stable components Vs and unstable components Vi, generated bythe extraction method P of the invention from a subject material element1 to provide firstly an identifier and secondly a one-time pad, and alsopublic and private keys of an asymmetric cryptographic protocol. Forthis type of use, the extraction method P is used a first time togenerate a random signature V of which one part Vi1 of the unstablecomponents is used as identifier, a second part Vi2 of the unstablecomponents is used as private key 31, whilst a third part Vi3 of theunstable components is used as public key 32. The private key 31 is thenused in an enciphering process 33 to obtain from identifier 30 a signedor enciphered identifier 34. One part of the stable components Vs isthen used as onetime key in an encrypting process 35, e.g. of XOR type,to obtain from signed identifier 34 a securitized signed identifier 36.Holding of the subject material element 1 and a device implementing theextraction method P of the invention then makes it possible to reaccessthe stable part Vs of the random signature V and hence to decrypt thesecuritized signed identifier 36 to access the signed identifier 34generated during the first use of the inventive method P for extractinga random signature.

FIG. 21 illustrates one use of the inventive extraction method under theprotocol for RSA encrypting with public key and private key. The randomsignature extracted from a subject material element is then used togenerate the strong prime numbers p and q. Number n is the product pq.Number e is an integer chosen to be prime with φ(n) while d is chosensuch that ed≡1 (mod φ(n)). The private key Cs then consists of integersp, q and d while the public key consists of integers n and e. If thenumber referenced 40 is an identifier to be encrypted then the numberreferenced 41 is this identifier encrypted by means of the RSA protocolusing the public Cp and private Cs keys above.

Evidently, the method for extracting a random signature according to theinvention may comprise different phases using at least part of thestable and unstable components in various processes for generating atleast one unique code and for ciphering this code.

Also, the methods of the invention may be used in many otherapplications without departing from the scope of the present invention.

1- Method for generating a decomposition base which can be used toextract a random signature from a subject material element, comprisingthe following steps: generating N acquisition vectors of structuralcharacteristics of at least one region of an at least one materialelement separate from the subject material element and/or from thesubject material element itself, analysing all the acquisition vectorsusing statistical methods to obtain the decomposition base formed ofdecomposition vectors enabling the representation of each acquisitionvector in the form of an image vector of which each componentcorresponds to the contribution of a decomposition vector in theacquisition vector, analysing at least part of the decomposition vectorsto identify that or those decomposition vectors, called common orcertain contribution decomposition vectors, which will be at the originof highly determinist and/common components to all image vectorsobtained using the decomposition base, saving the decomposition base,optionally saving a reading mask which, in the decomposition base, givesthe position of any decomposition vectors at the origin of deterministcomponents and/or the position of decomposition vectors at the origin ofrandom components. 2- Method for generating a decomposition base as inclaim 1, characterized in that analysis of the decomposition vectorscomprises the following steps: projecting each acquisition vector ontothe decomposition base to obtain an image vector of which each componentcorresponds to the contribution of a decomposition vector in theacquisition vector, analysing at least part of the image vectors toidentify that or those components which are highly determinist and/orcommon to all image vectors, the determinist components corresponding todecomposition vectors in the decomposition base called common or certaincontribution decomposition vectors, the other components of an imagevector being considered as random components. 3- Method for generating adecomposition base as in claim 1, characterized in that it is consideredthat a component has a highly determinist value if its value ispredictable in relation to the type of material element. 4- Method forgenerating a decomposition base as in claim 1, characterized in thateach acquisition vector is at least of two-dimensional nature. 5- Methodfor generating a decomposition base as in claim 1, characterized in thatit comprises a removal step to remove common or certain contributiondecomposition vectors from the decomposition base, and a step to savethe reduced decomposition base, called decomposition base into randomcomponents. 6- Method for generating a decomposition base as in claim 1,characterized in that the step to generate acquisition vectors is madewith at least one material element of the same family as the subjectmaterial element. 7- Method for generating a decomposition base as inclaim 1, characterized in that the step to generate acquisition vectorscomprises the following steps: generating a number N of acquisitions,according to an acquisition window, of structural characteristics of atleast one region of at least one material element separate from thesubject material element and/or of the subject material element itself,digitizing, along a scanning path, each of the acquisitions into theform of an acquisition vector. 8- Method for generating a decompositionbase as in claim 7, characterized in that it comprises a step to definethe geometric characteristics of the acquisition window. 9- Method forgenerating a decomposition base as in claim 7, characterized in that itcomprises a step to read the geometric characteristics of theacquisition window. 10- Method for generating a decomposition base as inclaim 7, characterized in that it comprises a step to save the geometriccharacteristics of the acquisition window. 11- Method for generating adecomposition base as in claim 7, characterized in that it comprises astep to define the characteristics of the scanning path. 12- Method forgenerating a decomposition base as in claim 7, characterized in that itcomprises a step to read the characteristics of the scanning path. 13-Method for generating a decomposition base as in claim 7, characterizedin that it comprises a step to save the characteristics of the scanningpath used for the digitization step. 14- Method for generating adecomposition base as in claim 1, characterized in that to obtain thedecomposition base it uses an algorithm of Principal Component Analysis.15- Method for generating a decomposition base as in claim 1,characterized in that to obtain the decomposition base it uses analgorithm of Independent Component Analysis. 16- Method for generating adecomposition base as in claim 1, characterized in that for theidentification of determinist components it uses a spectraldecomposition algorithm and identification of the certain contributiondecomposition vectors by filtering. 17- Method for generating adecomposition base as in claim 1, characterized in that each materialelement used is chosen from among: materials of dead biological origin,materials of organic origin, materials of mineral origin or materialsobtained by mixture and/or composition and/or deposit of several of thepreceding materials. 18- Method for extracting a random signature from asubject material element, comprising: a phase to generate at least oneacquisition vector of structural characteristics of at least one regionof the subject material element, a phase to generate at least one randomsignature vector from the acquisition vector, the random signaturevector comprising: a at least one random component having a stablenature so that its value may be found on each implementation of themethod on one same region of the subject material element, and/or atleast one random component having an unstable nature so that its valueis likely to vary random fashion on each implementation of the method onone same region of the subject material element, use of the randomsignature vector as random signature. 19- Method for extracting a randomsignature as in claim 18 characterized in that it comprises: applicationof a decomposition base, before the random signature generating phase, adecomposition phase of each acquisition vector according to thedecomposition base to obtain an image vector containing randomcomponents which each correspond to the contribution in the acquisitionvector of a decomposition vector belonging to the decomposition base,and in that each component of the random signature vector is obtained byextraction of and/or processing at least one random component of atleast one image vector. 20- Method for extracting a random signaturefrom a subject material element, comprising: application of adecomposition base, a phase to generate at least one acquisition vectorof structural characteristics of at least one region of the subjectmaterial element, a decomposition phase of each acquisition vectoraccording to the decomposition base to obtain an image vector containingrandom components which each correspond to the contribution in theacquisition vector of a decomposition vector belonging to thedecomposition base, a phase to generate at least one random signaturevector which contains the same number of components or less as thenumber of random components of each image vector, each component of therandom signature vector being obtained by extraction of and/orprocessing at least one random component of at least one image vector.use of the random signature vector as random signature. 21- Method forextracting a random signature as in claim 18, characterized in that,during the phase to generate a random signature vector, quantificationis performed so that each random component of the random signaturevector is able to present a finite number of values or levels. 22-Method for extracting a random signature as in claim 19, characterizedin that, during the phase to generate at least one acquisition vector, nacquisition vectors are generated of one same region of the subjectmaterial element, and in that n image vectors are used eachcorresponding to an acquisition vector. 23- Method for extracting arandom signature as in claim 22, characterized in that during the phaseto generate at least one random signature vector: quantification isperformed so that each random component of the random signature vectoris able to present a finite number of values or levels which correspondto statistical classes, the value or level of each component of therandom signature vector is defined by the result of the tests and/orstatistical processing applied to all the values of the component in agiven row of the n image vectors. 24- Method for extracting a randomsignature as in claim 23 characterized in that, during the phase togenerate at least one random signature vector, the components of theimage vectors undergo statistical processing consisting of theircentering reducing. 25- Method for extracting a random signature as inclaim 23, characterized in that during the phase to generate at leastone random signature vector: use is made of: a number C of statisticalclasses corresponding to values or levels able to be adopted by therandom components of the random signature vector, and a statisticalclass corresponding to the unstable nature of the components of one samerow of the n image vectors, to determine the value of each randomcomponent of the random signature vector, statistical processing isperformed and a statistical stability test of all the components of onesame row of the n image vectors so that: if after the stability test itappears that the components of this row of image vectors have a stablecharacter, then the value or level of the statistical class to which thecomponents of the same row of the n image vectors belong is assigned tothe random component of the random signature vector, if, after the test,it appears that the components of this row of image vectors have anunstable character, then the value or level of the statistical class towhich the component of the same row of one of the n image vectorsbelongs is assigned to the random component of the random signaturevector. 26- Method for extracting a random signature as in claim 25,characterized in that during the phase to generate at least one randomsignature vector, the stability test is performed on the basis of themean and standard deviation of the components in the same row of imagevectors. 27- Method for extracting a random signature as in claim 22,characterized in that the n acquisition vectors are generated virtuallyfrom a number of real acquisitions less than n. 28- Method forextracting a random signature as in claim 22, characterized in that then acquisition vectors are generated virtually from one real acquisition.29- Method for extracting a random signature from a subject materialelement, comprising: a phase to generate at least one acquisition vectorof structural characteristics of at least one region of the subjectmaterial element, a phase to generate at least one random signaturevector from the acquisition vector, the random signature vectorcomprising: at least one random component having a stable nature so thatits value may be found on each implementation of the method on one sameregion of the subject material element, and/or at least one randomcomponent having an unstable nature so that its value is likely to varyrandom fashion on each implementation of the method on one same regionof the subject material element, use of the random signature vector asrandom signature, characterized in that it comprises: application of adecomposition base, before the random signature generating phase, adecomposition phase of each acquisition vector according to thedecomposition base to obtain an image vector containing randomcomponents which each correspond to the contribution in the acquisitionvector of a decomposition vector belonging to the decomposition base,and in that each component of the random signature vector is obtained byextraction of and/or processing at least one random component of atleast one image vector, further characterized in that the methodcomprises a phase to generate the decomposition base according to themethod of claim
 1. 30- Method for extracting a random signature as inclaim 18, characterized in that the random signature vector comprises atleast one random component having a stable nature, the value of thisstable random component being able to be found on each implementation ofthe method on one same region of the subject material element. 31-Method for extracting a random signature as in claim 18, characterizedin that the random signature vector comprises at least one randomcomponent of unstable nature, the value of this unstable randomcomponent being likely to vary random fashion on each implementation ofthe method on one same region of the subject material element. 32-Method for extracting a random signature as in claim 18, characterizedin that all the random components of the random signature vector have astable nature able to be found on each implementation of the method onone same region of the subject material element. 33- Method forextracting a random signature as in claim 18, characterized in that allthe random components of the random signature vector have an unstablenature, the value of each unstable random component being likely to varyrandom fashion on each implementation of the method on one same regionof the subject material element. 34- Method for extracting a randomsignature as in claim 18, characterized in that during the generationphase of at least one random signature vector, the following aregenerated: a stable random signature vector whose random components havea stable nature, the value of each stable random component being able tobe found on each implementation of the method on one same region of thesubject material element, an unstable random signature vector whoserandom components have an unstable nature, the value of each unstablerandom component being likely to vary random fashion on eachimplementation of the method on one same region of the subject materialelement. 35- Method for extracting a random signature as in claim 18characterized in that: the random signature vector comprises: at leastone random component having a stable nature so that its value is able tobe found on each implementation of the method on one same region of thesubject material element, at least one random component which has anunstable nature so that its value is likely to vary random fashion oneach implementation of the method on one same region of the subjectmaterial element. during the generation phase of at least one randomsignature vector, a reading mask is generated giving the position in therandom signature vector of the stable random components and/or of theunstable random components. 36- Method for extracting a random signatureas in claim 18, characterized in that the phase to generate at least oneacquisition vector comprises the following steps: generating at leastone acquisition, according to an acquisition window, of structuralcharacteristics of one region of the subject material element,digitizing, along a scanning path, each acquisition into an acquisitionvector. 37- Method for extracting a random signature as in claim 36,characterized in that it comprises a step to define the characteristicsof the acquisition window. 38- Method for extracting a random signatureas in claim 36, characterized in that it comprises a step to define thecharacteristics of the scanning path. 39- Method for extracting a randomsignature as in claim 18, characterized in that it comprises a phaseusing at least part of the stable components of the random signature asidentifier of the subject material element or of an object associatedwith the subject material element in a process for controlling access.40- Method for extracting a random signature as in claim 18characterized in that it comprises a phase using at least part of thestable random signature as one-time pad in a cryptographic process. 41-Method for extracting a random signature as in claim 18 characterized inthat it comprises a phase using at least part of the stable randomsignature as sequence of instructions or as identifier of a sequence ofinstructions in a process to control an logic controller or machine. 42-Method for extracting a random signature as in claim 18 characterized inthat it comprises a phase using at least one part of the stable randomsignature as variables or parameters of a computer program. 43- Methodfor extracting a random signature as in claim 18 characterized in thatit comprises a phase using at least part of the stable random signatureas one-time pad to encrypt variables and/or executable parts of acomputer program. 44- Method for extracting a random signature as inclaim 18 characterized in that it comprises a phase using at least partof the unstable random components as identifier of the subject materialelement or of an object associated with the subject material element,and a phase using at least part of the stable random components asone-time pad for encrypting the identifier in order to obtain asecuritized identifier. 45- Method for extracting a random signature asin claim 18 characterized in that it comprises: a phase using at leastpart of the unstable random components as private key in a cryptographicprocess with public key/private key, a phase using at least part of thestable random components as one-time pad for encrypting the private keyto obtain a securitized private key. 46- Method for extracting a randomsignature as in claim 18 characterized in that it comprises: a phaseusing part of the unstable random components as private key in acryptographic process with public key/private key, a phase using part ofthe unstable random components as public key in the cryptographicprocess with public key/private key, a phase using at least part of thestable random components as one-time pad for encrypting the private keyto obtain a securitized private key. 47- Method for extracting a randomsignature as in claim 18 characterized in that it comprises: a phaseusing at least part of the unstable random components as identifier ofthe subject material element or of an object associated with the subjectmaterial element, a cipher phase of the identifier using a cryptographicprocess with public key/private key to obtain an enciphered or signedidentifier, a phase using at least part of the stable random componentsas one-time pad for encrypting the ciphered or signed identifier toobtain a ciphered, securitized identifier. 48- Method for extracting arandom signature as in claim 47, characterized in that part of theunstable random components is used as private key. 49- Method forextracting a random signature as in claim 47, characterized in that partof the unstable random components is used as public key. 50- Method forextracting a random signature as in claim 18 characterized in that itcomprises phases using part of the unstable random components and partof the unstable random components in ciphering processes. 51- Method forextracting a random signature as in claim 18 characterized in that itcomprises phases using at least part of the stable and unstablecomponents in processes to generate at least one unique code and toencipher this code. 52- Device comprising acquisition means, processingmeans and memory means, the processing and memory means at least beingadapted to implement the random signature extraction method according toclaim
 18. 53- Computer program being adapted to implement the randomsignature extraction method according to claim
 18. 54- Device comprisingacquisition means, processing means and memory means, the processing andmemory means at least being adapted to implement the method forgenerating a decomposition base according to claim
 1. 55- Computerprogram being adapted to implement the method for generating adecomposition base according to claim 1.